Scientists study the world to gather knowledge. Engineers utilize this knowledge to solve problems and create a better world. This blog is about using biological knowledge to engineer better gardens, more efficient systems, tastier foods, and, well, anything else I can think of.

Sunday, November 15, 2015

I like to fill every possible niche in my ecosystem. Whenever I see a hole, I start looking for the right organism to fill it. So when I started a garden with a big tank of water, I immediately started looking for plants that would grow in water. I started by pointedly ignoring watercress (blech!), then moved onto water chestnuts. I found some and grew them for a year and a half before I went to harvest them and found they had all rotted away. But I digress.

Really, the holy grail for me is edible greens that will grow through the summer here in Phoenix, AZ. I love greens and would prefer to eat a lot of them. The problem is, most greens, like spinach and all of the various lettuces, go immediately to seed as soon as it gets over 80 degrees. Kales tend to be bitter in the heat. Chard actually does pretty well, but I would like a little variety.

My search for edible plants to grow in the water led me to one that meets both goals. Water spinach is the American name for a semi-aquatic, vining plant native to southeast Asia. The scientific name is Ipomoea aquatica. Known as ong choy in China and kangkong (LOVE that one) in the Philippines, it has many names. It isn't actually related to spinach, though. Ipomoea is the family that also contains morning glory and sweet potatoes.

Water spinach has hollow stems that allow the plant to float on top of the water. An aggressive grower, it will spread across the top of whatever water you give it, forming a dense mat. It then shoots a thick canopy of leaves up above the water and a dense mat of roots down into the water up to two feet deep. In ideal conditions, which seem to be over 100 degrees Fahrenheit, full sun, and lots of non-stagnant water filled with abundant nitrogen from fish, it grows at an amazing rate. I have seen individual vines grow over a foot a day. I have harvested three pounds of leaves, leaving the plant looking picked completely clean, only for it to look like nothing at all happened four days later. It is far and away my most productive plant and I probably eat an average of 1/2-1 pound off of it a week, mostly as the greens for my morning smoothie.

While the flavor tastes quite like spinach, it is a little stronger, somewhere between spinach and kale. The texture isn't crispy like spinach nor tough like kale, though. It is more tender, like lettuce. About the last foot of the vine can also be eaten as well. The older vines are tough and somewhat woody, but the tender new growth is quite tasty when lightly stir-fried. Nutritionally, I haven't been able to find too much information, but it seems to be very similar to spinach.

One of my favorite parts is that it is also a favorite edible of my tilapia. Any leaves that dip down into the water are quickly nibbled off. They also eat the roots, having a particular fondness for them. I once caught a tilapia fingerling and brought it inside so I could watch it grow. On a whim, I pulled off some water spinach roots and brought them in. The fingerling rushed to the roots and took a bite, Then it swam around erratically in what I can only describe as a happy dance, then rushed back and took several more bites. I accidentally killed my water spinach last year about this time and started some new from seed this summer. The new plant is almost as big as the old one was, but it still doesn't have any noticeable roots. The fish in my tank keep them well trimmed. I figure it is only a matter of time before the plant develops enough of a mat that it will get ahead of the fish. In the meantime, it doesn't seem to be suffering at all.

There are a couple of precautions I would give. First, in its native habitat, the hollow stems are often a host for an intestinal parasite. The parasite isn't native to the United States, but be careful where you get your shoots. Or just start from seed. It is also considered an invasive and has become a problem in parts of Florida and Louisiana. So be careful where you grow it. As for my system, I really think that it is both an incredible boon and a bit of a nuisance. It grows in my main tank, and as such, gets first crack at the available nitrogen. I suspect the rest of my plants just get the little bit that is left after the water spinach is done. Also, while the floating mat provides great shelter for baby fish and shade in the heat of the summer, it also blocks access to oxygen exchange, necessitating an air pump if you have more than a few fish.

Overall, though, I highly recommend water spinach for any sort of aquaponics or similar system. It feeds the fish and gives a steady supply of fresh greens for you all summer long.

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Disclaimer

I am not an expert on any of the topics presented here, merely an enthusiastic hobbyist. I claim no responsibility for how this information is used and make no guarantees that it is completely accurate, only accurate to the best of my knowledge.